Alternating-current motor



Aug. 11, 1925/ F. PUNGA ALTERNATING CURRENT MOTOR Filed Aug. 16. 1920 TO STARTING SWITCH ROTOR,

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UNITED STATES PATENT OFFICE.

FRANKLIN PUNGA, 0F MULHEIM-RUHR-SPELDORF, GERMANY.

. ALTEENATING-CUBREN'I MOTOR.

Application filed August 16, 1920. Serial No. 404,033.

(GRANTED UNDER THE PROVISIONS OF THE ACT OF MARCH 3, 1921, 41 STAT. L, 1313.)

To all whom it may concern:

Be it known that FRANKLIN PUNGA, a

Duisburgerstr., Mulheim -Ruhr Speldorf, Germany, has invented certain new and useful Improvements in Alternating-Current Motors (for which I have filed applications in England,'April 10, 1920, No. 10,062; Germany, March 26, 1919, No. P 37,582; Germany, May 5, 1920; Spain, March 25, 1920 Holland, April 7, 1920, No. 14,460; France,f April 10,1920, No. 125,493; Belgium, April 13,1920, No. 229,012, and Poland," April 6,

- 1920, No. 5,094), of which the following is nating current motor for single or multi-- phase current, in which, for the purpose of" avoiding slip rings and starter, two -d1fier-' ent windings are provided in the rotor, one

a s ecification, reference being had therein to t e accompanying drawing;

The subject of the invention 18 an alter-.

a winding which remains constantly short 'circuited and is provided with relatively high ohmic resistance (starting winding), and a second windin with relatively low ohmic resistance, whic is short circuited by a special switching device only after starting (running winding). 'In previously known motors, the generation of a high self inductance in the rotor has been found to. be

for the purpose of decreasing the shock o the current on switching in. t

According to the present invention, this self inductance is generated by increasing the doubly interlinked or zigzag "leakage (see Abhandlung von Rogowskl und Simons in the Elektrotechnische Zeitschrift 1908,

ages 535 and 564:, and -Abhandlungen .vonungain the Archiv fiir Elektrotechnik,

Vol. VII,- Numbers 11 and 12), whereas in the known constructions this self inductance is obtained by increasing the singly inter- I linked or slot leakage. The increase of the of slots for normal running and for starting is preferably obtained by arranging the starting winding in. a fewernumber of r'otor 4 slots than those occupied by running wind;

, ings.

citizen of Germany, residing at No. 466

Obviously an equivalent of the essence of only very small portions (for instance a;

small number of coils), whereas the major portions coils) 8.18'111 the others. I

An example of carryin out is shown diagrammatica 1y panying drawing, in which the invention the accom- Fig. 1 is a diagrammatic sectional view of a motor embodying the invention.

Fig. 2 is a similar view of a modification. Fig.3 shows the windings in connection with a special switching contrivance. Fig. 4 is a front elevation, partly in section of a modified form of switch, the same belng shown in the open position. I V

Fig. -5 is a transverse section thereof, showing the parts in position with both windings connected up, and

Fig. 6 is a side elevation of the same.

The winding a isthe running winding, which is to become operative only after starting and is short-circuited by any de sired means. In Fig. 3 of the drawings is shown a well known short-circuiting device d for this purpose. For the starting winding, a cage armature with bars 6 is shown for example, which has been designed for (for instance a large number of relatively large slip at normal load. The

bars 6, as shown in Figs. 1 and 2, are less in number than the bars a. As shown there is a. bar I) in each alternate slot in Fig. 1, while in Fig. 2 each alternate slot is deep enough toaccominodate a winding a only while each other slot is of a. depth suflicient 4 to accommodate a winding a and a bar 6.

Preferably *the. winding a is in proximity to the; air gap, and the winding b nearer the axis of the rotor, in order that the leak age produced by the windin a (that is, the

leakage during running) wi be as small as possible, and the leakage produced by the winding 22 (that is, the leakage during starting) be as great as possible.

The rotor slots can be either all uniformly formed, as shown in Fig. 1, and the portions o f the slots, which do not carry bareb, can i be used for ventilation, or, when such ventilation is not required additional slots for the starting winding can at intervals be formed simultaneously as shown in Fig. 2.

The form of slots shown in Fig. 2, gives, in addition to the increase of the doubly interlinked leakage, a further advantage. The concentration of the bars of the starting winding in a smaller number of slots elfects a considerable increase in the eddy current loss in the winding a on starting, a phenomenon which can be advantageously utilized for starting, for the reason that the resistance of the rotor winding becomes smaller in proportion as the speed of revolution approaches synchronism.

The bars I) rest tightly in the slots preferably without insulating, so that the heat enerated can be easily given up to the iron body of the rotor. The connection of the bars to the end rings is preferably effected by welding, whereby the danger of disconnection when running will be practically eliminated. It is preferable to utilize the clamping discs of the rotor as the end rings, whereby the construction may be cheapened. With the use of iron clamping discs and iron bars the skin effect of such discs can be utilized to advantage.

Instead of arranging the running and starting windings in slots in common, as shown in Fig. 1, they can also be arranged in different slots adjacent to one another as shown in Fig. 2, for example. In the latter case the starting Winding will remain active even during running which in the arrangement shown in Fig. 1 is the case to a minor degree only.

The rotor, in the embodiment of the in vention illustrated, is mounted concentrically within a stator A having a winding or windings B, as is common.

In Fig. 3 is illustrated a simple form of device for switching the rotor. When the lever 7, is in the full line position the rotor is cut out. When in the dotted line position the short circuiting device (1 is closed by means of the link m and rotating rod 12. Current may be admitted to the stator A by means of any desired switching device.

The advantage of the form of switch shown in Figs. 4, 5 and 6 is that the running winding cannot be switched in until after the stator winding has been switched in, and on the other hand the short circuiting of the running winding is positively dependent on and follows the switching out of the stator winding. The necessity of switching in the running winding after the switching in of the stator winding' has been accomplished is due to the nature of the above describedalternating current motor. The said constrained sequence on switching out is of inn-- portance, in order to avoid the formation of fused beads on the contact of the shortcircuiting switch. The switch shown in the modification is accordingly so arranged, that between the switching in of the stator winding and the switching in of the running winding a lapse of time occurs, during which the motor approximately picks up full speed, whereby the switching in of the running winding is rapidly effected.

In the modification shown in Figs. 4, 5 and G, the said constrained sequence of the switching operations is effected by one complete revolution of a switch drum, the direction of rotation of which is irreversible. On a switch. drum 7', which is rotated by a crank 7' provided with an indicator disc 9, are provided contact strips 8, which interconnect spring contacts 6 and f of the serv ice terminals g and the stator terminals 7t, when in a suitable angular position, for instance that of Fig. An arm p, pivotally connected to the link m of the short-circuiting device n, d (Fig. 3) of the running winding, is mounted on the spindle of the switch drum by means of a crank or eccentric o in the spindle. .On the spindle of the switch drum 7' is also secured a detent disc 2' having three detent notches 71: and Z1 in which successively engages a detent spring 2,. In the open position shown in Fig. 4, the detent spring engages in the notch 70 when the contacts 6 and f and the short-circuiting device a, d are out. On turning the crank 9* from the notch 70 to the notch 70', the stator winding is switched in by interconnection of the contacts e and f by means of the contact strip a, whilst the shcrt-circuiting device does not yet become operative. The necessary stroke of the crank or eccentric 0 for switching in the short-circuiting' device, occurs only on transit from the notch 70 to the notch in".

The notch 7% serves therefore for the running position. Switching out results by further cranking through 180" from the notch 70 to the notch 70 at the beginning of which the stator winding is switched out by breakof contact at the contacts 6 and f, whilst only during the ensuing course of the rotation, the switching out of the shortcircuit winding is'elfected by the crank or eccentric 0.

I desire to have it understood thatmy invention may be carried out in connection with single or multiphase alternating current or induction motors:

I claim:

1. An alternating current motor, comprising a rotor having winding slots therein there being a running winding in each of said. slots, and there being a starting windin in a. less number of said slots.

An alternating current motor, comprising a rotor having winding slots therein, there being a running winning in each ofv said slots, and there being a starting winding in a less number of said slots, said starting winding being in proximity to the running winding in 1ts slot.

3. An alternating current motor, comprising a rotor and a stator, said stator having a winding, separate starting and running windings carried by the rotor in separate concentric circular series, each rotor winding comprising a plurality of bars, the angular distance between the runnin winding bars being less than the angular distance between the starting winding bars, the startin winding being permanently short circuite means for short circuiting the running winding after starting the motor, means for switching in the windings, the means for switching in the running winding following the prior switching in of the stator windin and the switching out of the running win ing following the prior switching out of the stator winding.

4. An alternating current motor, comprising a rotor of sriuirrel-cage formation, a plurality of equa ly spaced winding bars arranged longitudinally of the rotor and formin the periphery thereof, a plurality of win ings arrange parallel to the first mentioned bars and in circular arrangement between the first mentioned bars and the axis of the rotor, each of said second mentioned bars bein in proximity to an alternate one of said first mentioned bars.

In testimony I have afiixed my si ature.

FRANKLIN P GA. 

